Lindian Resources Ltd (ASX:LIN) has achieved a concentrate grade of 60% rare earth oxides (REO) in phase one metallurgical test-work at its Kangankunde Rare Earths project in Malawi.
During the program, the company confirmed that water-only, low-cost gravity and magnetic beneficiation techniques are suitable for the Kangankunde mineralisation.
These results build on the historical metallurgical work undertaken in the 1970s by Lonrho that reported a REO recovery of 60% to a mineral concentrate bearing 60% REO.
Lindian continues to refine the use of gravity and magnetic separation techniques and expects to further improve the REO recovery and REO concentrate grade, with finer grinding a key variable to be tested to improve recovery and concentrate grade.
Moving forward, these early-stage initial results look promising and will be used to guide the ensuing metallurgical optimisation program.
“Exceptionally pleasing”
Lindian CEO Alistair Stephens said: “These early-stage results are exceptionally pleasing and deliver excellent concentrate grades and recoveries from this initial metallurgical test-work.
"The results benchmark us very well when compared to some of the world’s notable rare earths projects.
"Importantly, this work builds on the historical metallurgical work that was undertaken in the 1970s by Lonrho that reported an REO recovery of 60% to a mineral concentrate bearing 60% REO.
"Furthermore, new gravity recovery technologies – particularly the Multi Gravity Separator (MGS), which was not developed at the time these historical works were undertaken – present an avenue for improved metallurgical recovery.
"Also, the use of modern vertical-ring wet high-intensity magnetic separators (WHIMS) over the dry Induced Roll High Intensity (IRHI) magnetic separators used in the historical work to further upgrade a gravity concentrate promises greater practicality in the process by eliminating costly dewatering and drying steps from the process.”
Test work highlights
Lindian’s initial evaluation of the MGS demonstrates that recovery of fine-grained rare earth mineralisation is enhanced over that achieved using a shaking table, with MGS achieving a 69.7% LREO recovery to a concentrate grading 51.7% LREO in one pass on a -53µm fines sample.
Recovery ranges for rougher and cleaner stages of shaking table test work on coarser (+53µm) fractions range from 60% to 90%.
Preliminary wet high-intensity magnetic separation (WHIMS) testing has demonstrated increases in the REO grade of a final concentrate to near 60% REO
Stephens adds: “The results of the MGS testing warrant further emphasis. For a single machine – in one pass – to produce an REO concentrate exceeding 50% TREO with a metallurgical recovery approaching our target of 80% is truly remarkable and presents the company with various options and processing flexibilities for its Phase 1 plant.
“The company has secured the use of the only MGS test machine in Perth, where it will undertake extensive further testing, including variability testing.
“This scoping work has validated a general process scheme for Kangankunde, with several significant avenues for improvement identified.”
MGS testing.
Forward plan
Further metallurgical testing and optimisation will be undertaken to appropriately define the metallurgical processing scheme and provide metallurgical metrics for the design of a phase one plant, including:
- comminution, bulk milling and classification testing,
- spiralling and shaking table testing,
- evaluation of enhanced gravity concentrators, including the Multi-Gravity Separator (MGS) and Falcon concentrator,
- WHIMS testing,
- REO product and tailings product characterisation, and
- metallurgical variability testing.
In the course of undertaking this work, the metallurgical process scheme will be optimised and a more accurate provision of processing metrics determined.
Stephens adds: “These results are being used to guide the optimisation metallurgical testing program for the definition of the process flowsheet and process metrics – which is considered simple in comparison to the overwhelming majority of other REE projects – for the planned Stage 1 rare earths concentrate processing plant at Kangankunde.
“Metallurgy is another critical aspect of the project that is key to bringing Kangankunde into production. Just like our development drilling program, metallurgical test-work is ongoing and we look forward to reporting more results as the program advances.”